"When you say your job building buildings is akin to our sacrifice, you are attacking our sacrifice."

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Khizr Khan, father of fallen US Army Capt. Humayun S. M. Khan, holds up his copy the United State Constitution as he speaks during the final day of the Democratic National Convention in Philadelphia , Thursday, July 28, 2016.

Families of 11 U.S. service members who died fighting for their country signed a letter demanding an apology from Donald Trump for trivializing the sacrifices their loved ones made, NBC News reported.

Trump questioned why Ghazala Khan stood by quietly at the DNC as her husband Khizr Khan talked about their son Humayun, who died in Iraq.

The letter called Trump's comments "repugnant, and personally offensive." "When you question a mother's pain, by implying that her religion, not her grief, kept her from addressing an arena of people, you are attacking us," the Gold Star letter added. "When you say your job building buildings is akin to our sacrifice, you are attacking our sacrifice."

Families that have lost members are known as Gold Star families. The letter was organized by Gold Star Mother Karen Meredith from VoteVets.org, an advocacy group that calls itself non-partisan but which has been described in the past as allied to Congressional Democrats. The Center for Responsive Politics says VoteVets.org is fueled "largely by social welfare organizations aligned with Democrats and millions of dollars given by unions."